1. Field of the Invention
The present invention relates to a semiconductor integrated circuit and a method for controlling the semiconductor integrated circuit.
2. Related Art
Recently, semiconductor memories have come to operate on lower voltages and at higher speeds increasingly. This has led to a desire that a sense amplifier and a pre-charge circuit which are used to read signals from the semiconductor memory may also operate faster on a lower voltage.
As a current difference sense type of a sense amplifier operating on a lower voltage, a circuit equipped with a differential amplifier and a current source for the differential amplifier is used. The sense amplifier has its input line connected to a bit line for memory cells and its reference line connected to a reference bit line for reference cells. This type of the sense amplifier is arranged to pre-charge the input line and the reference line by using the current source and then sense a differential current between the memory cell and the reference cell by using the differential amplifier.
This sense amplifier may be unstable in sensing if an excessive current flows through the differential amplifier. Accordingly, to secure the stability in sensing, it is necessary to limit current driving capability by setting a longer channel length L of a MOS transistor that operates as the current source. However, the MOS transistor is used also in pre-charging, thus leading to a problem in that a smaller applicable current may prolong a pre-charge time.
It is to be noted that as the sense amplifier, such a circuit is known as to be described in, for example, Japanese Patent Application Laid-Open No. 2007-35124.